Conventional precast concrete stairways exhibit a number of disadvantages. Very often, such stairs are constructed in a form or mold that has a step-shaped bottom surface for defining the steps and an open upper end into which the concrete is poured. This form creates a stairway that exhibits a heavy flat slab along its bottom surface. Such a stairway requires unnecessarily large amounts of concrete and is quite heavy. Moreover, because the bottom of the mold forms the steps, it is impossible to add a hardening or wear resistant material to the steps as they are forming in their wet condition. Such stair systems are also quite inflexible. The dimensions of each step form typically cannot be adjusted to match desired floor and building heights. A completely new form is required for each variation in height.
A stair system utilizing individually precast steps is known. In that system, steps are formed and then permanently cast into a pair of supporting side walls. Accordingly, worn or defective steps cannot be conveniently removed and replaced. Moreover, these steps are formed in an enclosed mold which, again, does not permit the addition of hardening or wear resistent materials to the concrete being cast. Additionally, this system does not permit the adjustment of tread depth and lateral width as well as riser height and width. And, as with many other precast stair systems, this stairway exhibits an inadequate fire rating due to its relatively thin steps. Many fire codes currently require a fire rating of at least two hours.